KR100349992B1 - Hydraulic system - Google Patents

Description

Hydraulic system

Field of invention

The present invention relates to a hydraulic apparatus, and more particularly, to a hydraulic apparatus including a hydraulic motor and a mechanical brake assembly for braking the hydraulic motor, for example, adapted to a drive device of a crawler vehicle.

Description of the prior art

Conventional hydraulic devices are disclosed in, for example, Japanese Patent Laid-Open No. 4-138960, and include a hydraulic pump 210, a hydraulic motor 220, a mechanical brake assembly 230, a directional control valve 240, a counterbalance valve ( 250, pilot hydraulic circuit 260, storage tank 271, relief valve 272, check valves 273-277, and restrictors 278, 279 are shown in FIG.

The hydraulic pump 210 sucks the working fluid stored by the storage tank 271 and increases the pressure to send the working fluid. The hydraulic motor 220 is a fixed displacement axial piston motor and has an output rotating shaft (not shown) mechanically connected to the drive shaft (not shown) of the crawler vehicle.

The hydraulic motor 220 includes a motor casing (not shown) formed by the first and second inlet / outlets 221 and 222. The working fluid is supplied from the hydraulic pump 210 to one of the first and second inlet / outlets 221, 222 through one of the first and second fluid supply / discharge passages 281,282 and the first and second inlet / outlet ( 221, 222 is discharged to the storage tank 271 through the other of the first and second fluid supply / discharge passages (281, 282). When the working fluid from the hydraulic pump 210 is received by the first inlet / outlet 221 of the hydraulic motor 220, the output shaft of the hydraulic motor 220 is rotated in one direction. When the working fluid from the hydraulic pump 210 is received by the second inlet / outlet 222 of the hydraulic motor 220, the output shaft of the hydraulic motor 220 is rotated in the opposite direction.

The mechanical brake assembly 230 is engaged with the output rotating shaft of the hydraulic motor 220 through a pair of friction pads fixed to the motor casing of the hydraulic motor 220 and the output rotating shaft of the hydraulic motor 220, respectively. ). The mechanical brake assembly 230 is a brake for elastically pressurizing the brake piston 231 to engage the cylindrical casing 232 and the output shaft of the hydraulic motor 220 to have the brake piston 231 slidingly received therein. It further includes a spring 233. The brake piston 231 and the cylindrical casing 232 of the mechanical brake assembly 230 are supplied with a working fluid through the fluid opening passage 283 and a hydraulic chamber 234 through which the working fluid is discharged through the fluid opening passage 283. To form together. The pressure of the working fluid in the hydraulic chamber 234 is applied on the effective area of the brake piston 231 so that the brake piston 231 is disengaged from the output shaft of the hydraulic motor 220 with respect to the elastic force of the brake spring 233. All. In the mechanical brake assembly 230 configured as described above, the output shaft of the hydraulic motor 220 is the brake spring (231) through the brake piston 231 when the working fluid is discharged from the hydraulic chamber 234 through the fluid opening passage 283 233 is mechanically braked by the elastic force. Conversely, when the working fluid is supplied to the hydraulic chamber 234 through the fluid opening passage 283, the rotating shaft of the hydraulic motor 220 is released from the brake piston 231 by the pressure of the working fluid in the hydraulic chamber 234. Therefore, both sides are freely rotatable in different directions.

The direction control valve 240 is provided on the first and second fluid supply / discharge passages 281 and 282 and acts to determine different direction control valve positions according to the manual operation of the caterpillar vehicle driver. Three different control valve positions allow the working fluid to be supplied from the hydraulic pump 210 to the first fluid supply / discharge passage 281 and discharge from the second fluid supply / discharge passage 282 to the storage tank 271. A first directional control valve position 240a, which may become a second directional control valve position where the working fluid may be discharged from the first and second fluid supply / discharge fluid passages 281 and 282 to the storage tank 271 ( 240b), and a third directional control valve position where the working fluid may be supplied from the hydraulic pump 210 to the second supply / discharge passage 282 and may be discharged from the first fluid supply / discharge passage 281. 240c.

The counter balance valve 250 is provided on the fluid opening passage 283 and the first and second fluid supply / discharge passages 281 and 282 between the hydraulic pump 210 and the control valve 240. On the first fluid supply / discharge passage 281, the counter balance valve 250 is arranged in parallel with the check valve 273, in which the working fluid is supplied from the directional control valve 240 to the hydraulic motor 220 only. It is suitable to flow only to). Similarly, the counter balance valve 250 is arranged in parallel with the check valve 274 on the second fluid supply / discharge passage 282, in which the working fluid is supplied from the directional control valve 240 to the hydraulic motor ( It is suitable to flow only to 220). The counter balance valve 250 acts on three different counter balance valve positions depending on the difference in pressure between the pilot hydraulic chamber 251 and the pilot hydraulic chamber 252. The counter balance valve position allows the working fluid to flow in the first fluid supply / discharge passage 281 between the hydraulic motor 220 and the directional control valve 240 and the hydraulic motor 220 and the directional control valve 240. The first and second counter balance valve positions 250a and 250b which are allowed to flow in the second fluid supply / discharge passage 282 therebetween, and the working fluid are the hydraulic motor 220 and the directional control valve 240. A third to block flow in the first fluid supply / discharge passage 281 between and to block flow in the second fluid supply / discharge passage 282 between the hydraulic motor 220 and the directional control valve 240. It consists of the counterbalance valve position 250c.

The fluid opening passage 283 causes fluid communication with the first fluid supply / discharge passage 281 when the counterbalance valve 250 is displaced to determine the first counterbalance valve position 250a.

The fluid opening passage 283 causes fluid communication with the second fluid supply / discharge passage 282 when the counterbalance valve 250 is displaced to determine the second counterbalance valve position 250b.

The fluid open passage 283 causes fluid communication with the fluid discharge passage 284 when the counterbalance valve 250 is displaced to determine the second counterbalance valve position 250b. The pilot hydraulic chamber 251 of the counterbalance valve 250 is supported in fluid communication with the first fluid supply / discharge passage 281 via the restrictor 278 and the check valve 276 arranged in parallel with each other. It is.

In the same manner, the pilot hydraulic chamber 252 is supported in fluid communication with the second fluid supply / discharge passage 282 via the restrictor 279 and the check valve 277 arranged in parallel with each other. The pilot hydraulic circuit 260 includes a check valve 261 and a restrictor 262 provided on the fluid opening passage 283 in parallel with each other.

The conventional hydraulic device thus configured operates as described below.

When the directional control valve 340 operates to determine the first directional control valve position 240a, the counterbalance valve 250 is displaced to determine the first counterbalance valve 250a and as a result the high pressure working fluid is hydraulic It is supplied from the pump 210 to the inlet / outlet of the hydraulic motor 220.

At the same time, the high pressure working fluid is supplied from the hydraulic pump 210 to the hydraulic chamber 234 of the mechanical brake 230 via the restrictor 262 of the pilot hydraulic circuit 260 so that the brake piston 231 is mechanical. The elastic force of the brake spring 233 of the brake assembly 230 is disengaged from the output shaft of the hydraulic motor 220. As a result, the output shaft of the hydraulic motor 220 rotates so that the drive shaft of the crawler vehicle has the driving force.

When the direction control valve 240 is operated to determine the second direction control valve position 240b, the working fluid in the first and second fluid supply / discharge passages 281 and 282 is discharged to the storage tank 271 and the pressure is reduced. .

At the same time, the working fluid in the hydraulic chamber 234 of the mechanical brake assembly 230 is discharged to the storage tank 271 through the fluid opening passage 283 and the first fluid supply / discharge passage 281, and thus the hydraulic motor 220. ) Is rotated by the brake spring 233 of the mechanical brake assembly 230 to stop. At this time, if the output rotation shaft of the hydraulic motor 220 rotates at a high speed and continues to rotate for a while, the hydraulic motor 220 serves as a hydraulic pump.

In this case, the counter balance valve 250 is the third counter due to the pressure of the working fluid in the pilot hydraulic chamber 251 maintained at a high pressure by the restrictor 278 compared to the pressure in the pilot hydraulic chamber 252 for a while. Displaced to determine the balance valve 250. This is blocked by the check valve 273 and the counterbalance valve 250 from the working fluid flows in the first fluid supply / discharge passage 281 between the hydraulic motor 220 and the counterbalance valve 250, The hydraulic resistance is provided to the hydraulic motor 220. As a result, the output shaft of the hydraulic motor 220 is braked by the mechanical braking force according to the brake spring 233 of the mechanical brake assembly 230 and the hydraulic braking force generated by the operation of the counterbalance valve 250.

However, the conventional control apparatus is accompanied by the drawback that when the crawler vehicle is stopped, for example, it receives a large shock generated by a deceleration exceeding 0.4 g (gravity acceleration). More specifically, the mechanical brake assembly 230 is used as a braking system for keeping the crawler vehicle stationary as well as a braking system for keeping the crawler vehicle stationary.

This means that the brake spring 233 of the mechanical brake assembly 230 is required to have a very strong elasticity. As a result, the brake spring 233 decelerates the crawler vehicle very quickly when the mechanical brake 30 is in an active state, so that the crawler vehicle is subjected to an extremely strong impact.

The present invention provides a hydraulic system that overcomes the disadvantages of conventional hydraulic systems having the general characteristics described above.

Summary of the Invention

A storage tank for storing the working fluid, a hydraulic pump for sucking the working fluid from the storage tank to discharge the working fluid by increasing the pressure, the first and second inlet / outlet and the output shaft, the working fluid has a first and The hydraulic pump is supplied from one of the first and second inlet / outlets through one of the second fluid supply / discharge passages and the first through the other of the first and second fluid supply / discharge passages And a discharge from the other one of the second inlet / outlet to the storage tank, and the output rotating shaft rotates in one direction when the working fluid from the hydraulic pump 54 is received by the first inlet / outlet. The output shaft is a hydraulic motor to rotate in the opposite direction when the working fluid from the hydraulic pump is received by the second inlet / outlet, the hydraulic motor And a brake piston engageable with the output rotation shaft, the cylindrical casing has a brake spring for resiliently pressing the brake piston to engage the output rotation shaft of the hydraulic motor and the brake piston that is slidably accommodated, and the brake The piston and the cylindrical casing jointly form a main hydraulic chamber through which the working fluid is supplied through the fluid opening passage, and the working fluid is discharged through the fluid opening passage, and the brake piston is a pressure of the working fluid in the main hydraulic chamber. And a first piston area portion applied to disengage the brake piston from the output rotation shaft of the hydraulic motor with respect to the elastic force of the brake spring, wherein the output rotation shaft of the hydraulic motor has a working fluid mechanical brake. When discharged from the main hydraulic chamber of the brake assembly, the brake is mechanically braked by the elastic force of the brake spring through the brake piston, and the output shaft of the hydraulic motor is supplied with a working fluid to the main hydraulic chamber of the mechanical brake assembly. And a mechanical brake assembly to release from the brake piston by the fluid pressure of the working fluid in the main hydraulic chamber, and the fluid opening passage, optionally in fluid communication with the first and second fluid supply / discharge passages. And a working fluid in one of the first and second fluid supply / discharge passages provided on the first and second fluid supply / discharge passages and in fluid communication with the fluid open passage. Pressure is greater than that of the other working fluid in the second fluid supply / discharge passage. A shuttle valve to be raised, provided on the first and second fluid supply / discharge passages, and a working fluid is supplied from the hydraulic pump to the first fluid supply / discharge passage and the second fluid supply / discharge passage A first directional control valve position to be discharged from the passage to the storage tank, a second directional control valve position to allow the working fluid to be discharged from the first and second fluid supply / discharge passages to the storage tank, and a working fluid Determine three different directional control valve positions comprising a third directional control valve position to be supplied from the hydraulic pump to the second fluid supply / discharge passage and to be discharged from the first fluid supply / discharge passage. An actuating directional control valve, provided on the first and second fluid supply / discharge passages between the hydraulic pump and the directional control valve, The hydraulic fluid is pressurized by the hydraulic motor to one of the first and second fluid supply / discharge passages when the hydraulic motor is operating while the direction control valve is displaced to determine the second direction control valve position. A hydraulic system composed of a counterbalance valve actuated to prevent the pressure of the brake, wherein the brake piston and the cylindrical casing further form a secondary hydraulic chamber maintained in fluid communication with the fluid open passage through the fluid transfer / return passage. The brake piston has a second piston area portion for applying pressure of the working fluid in the secondary hydraulic chamber to counteract the elastic force of the brake spring and allows the hydraulic system to restrict the flow of working fluid in the fluid transfer / return passage. Brakes provided on the fluid transfer / return passages for The hydraulic system further includes a restrictor is provided according to one aspect of the invention.

A storage tank for storing the working fluid, a hydraulic pump for sucking the working fluid from the storage tank to discharge the working fluid by increasing the pressure, the first and second inlet / outlet and the output shaft, the working fluid has a first and Supplied from one of the first and second inlet / outlet ports from the hydraulic pump through one of the second fluid supply / discharge passages and the first through the other of the first and second fluid supply / discharge passages. And a discharge from the other of the second inlet / outlet to the storage tank, and the output rotating shaft rotates in one direction when the working fluid from the hydraulic pump is received by the first inlet / outlet, and the output rotating shaft is A hydraulic motor to rotate in the opposite direction when the working fluid from the hydraulic pump is received by the second inlet / outlet; And a brake piston engageable with the output rotation shaft, the cylindrical casing has a brake spring for resiliently pressing the brake piston to engage the output rotation shaft of the hydraulic motor and the brake piston that is slidably received, and the brake The piston and the cylindrical casing jointly form a main hydraulic chamber through which the working fluid is supplied through the fluid opening passage, and the working fluid is discharged through the fluid opening passage, and the brake piston is configured to pressurize the pressure of the working fluid in the main hydraulic chamber. And a first piston area portion applied to disengage the brake piston 47 from the output rotation shaft of the hydraulic motor with respect to the elastic force of the brake spring, and the output rotation shaft of the hydraulic motor has a working fluid mechanical. The machine is braked by the elastic force of the brake spring through the brake piston when discharged from the main hydraulic chamber of the brake assembly, and the output shaft of the hydraulic motor is supplied when a working fluid is supplied to the main hydraulic chamber of the mechanical brake assembly. The first and second to have a mechanical brake assembly released from the brake piston by the fluid pressure in the main hydraulic chamber, the first and second fluid supply / discharge passages and the fluid opening passage optionally maintained in fluid soft tone; A working fluid in one of the first and second fluid supply / discharge passages provided on the second fluid supply / discharge passage and in fluid communication with the fluid open passage is provided in the first and second fluid supply / discharge passages. Shuttle valves allow for higher pressure than working fluid in the other one of the discharge passages And the first and second fluid supply / discharge passages, and a working fluid is supplied from the hydraulic pump to the first fluid supply / discharge passage and the storage tank from the second fluid supply / discharge passage. A first directional control valve position to be discharged to the second directional control valve position, a second directional control valve position to allow the working fluid to be discharged from the first and second fluid supply / discharge passages to the storage tank, and a working fluid from the hydraulic pump A direction control valve operative to determine three different direction control valve positions consisting of a third direction control valve position to be supplied to said second fluid supply / discharge passage and to be discharged from said first fluid supply / discharge passage; And on the first and second fluid supply / discharge passages between the hydraulic pump and the direction control valve. A counter operative to prevent pressurization of the working fluid by the hydraulic motor into one of the first and second fluid supply / discharge passages when the hydraulic motor is operating under displacement to determine a second directional control valve position A hydraulic system composed of a balance valve, wherein the brake piston and the cylindrical casing further form a secondary hydraulic chamber maintained in fluid communication with the storage tank through a fluid transfer / return passage. And a second piston area portion for applying pressure of the working fluid in the chamber to counteract the elastic force of the brake spring, wherein the hydraulic system is configured to restrict the flow of the working fluid in the fluid transfer / return passage. In the hydraulic pressure further comprising a brake resistor lister provided on the A stem is provided according to another aspect of the present invention.

A storage tank for storing the working fluid, a hydraulic pump for sucking the working fluid from the storage tank to discharge the working fluid by increasing the pressure, the first and second inlet / outlet and the output shaft, the working fluid has a first and One of the first and second inlet / outlets is supplied from the hydraulic pump through one of the second fluid supply / discharge passages and the other of the first and second fluid supply / discharge passages 58 and 59 is Is discharged to the storage tank from the other of the first and second inlet / outlet through the output shaft is rotated in one direction when the working fluid from the hydraulic pump is received by the first inlet / outlet, The output shaft is a hydraulic motor that rotates in the opposite direction when the working fluid from the hydraulic pump is received by the second inlet / outlet, the hydraulic motor And a brake piston engageable with the output rotation shaft, the cylindrical casing has a brake spring for resiliently pressing the brake piston to engage the output rotation shaft of the hydraulic motor and the brake piston that is slidably received, and the brake The piston and the cylindrical casing jointly form a main hydraulic chamber through which the working fluid is supplied through the fluid opening passage, and the working fluid is discharged through the fluid opening passage, and the brake piston is a pressure of the working fluid in the main hydraulic chamber. And a first piston area portion applied to disengage the brake piston from the output rotation shaft of the hydraulic motor with respect to the elastic force of the brake spring, wherein the output rotation shaft of the hydraulic motor has a mechanical fluid. Mechanically braked by the resilient force of the brake spring through the brake piston when discharged from the main hydraulic chamber of the brake assembly, and the output shaft of the hydraulic motor has a working fluid to the main hydraulic chamber of the mechanical brake assembly. The first brake to have a mechanical brake assembly which is released from the brake piston by the fluid pressure in the main hydraulic chamber when supplied, and the fluid opening passage, optionally in fluid communication with the first and second fluid supply / discharge passages. A working fluid in one of the first and second fluid supply / discharge passages provided on the first and second fluid supply / discharge passages and maintained in fluid communication with the fluid open passage is provided in the first and second fluids. Shuttle valves with a higher pressure than the working fluid in the other of the supply / discharge passages, It is provided on the first and second fluid supply / discharge passage, the working fluid is to be supplied from the hydraulic pump to the first fluid supply / discharge passage and discharged from the second fluid supply / discharge passage to the storage tank A first directional control valve position adapted to be discharged, a second directional control valve position such that a working fluid is discharged from the first and second fluid supply / discharge passages to the storage tank, and a working fluid is provided from the hydraulic pump; A directional control valve operative to determine three different directional control valve positions consisting of a third directional control valve position adapted to be supplied to a second fluid supply / discharge passage and to be discharged from the first fluid supply / discharge passage; It is provided on the first and second fluid supply / discharge passage between the hydraulic pump and the direction control valve, the direction control valve is the second direction A counterbalance valve which operates to prevent pressurization of the working fluid by the hydraulic motor as one of the first and second fluid supply / discharge passages when the hydraulic motor is operating under displacement to determine the control valve position. A hydraulic system configured, wherein the brake piston and the casing further form a secondary hydraulic chamber, the brake piston applying a second piston to apply pressure of the working fluid in the secondary hydraulic chamber to counteract the elastic force of the brake spring. Having an area portion, the hydraulic system is provided on the first and second fluid supply / discharge passages 58 and 59, and a working fluid is connected to the first fluid supply / discharge passage via the fluid transfer / return passage; Flow between the secondary hydraulic chamber and supply / discharge the second fluid through the fluid transfer / return passage A first selector valve position at which flow is interrupted between a passage and the secondary hydraulic chamber, a working fluid between the first fluid supply / discharge passage and the secondary hydraulic chamber via the fluid transfer / return passage and the The second selection valve position and the working fluid which block the flow between the second fluid supply / discharge passage and the secondary hydraulic chamber are connected to the second fluid supply / discharge passage and the secondary through the fluid transfer / return passage. Determine three different valve positions comprising a third selector valve position to flow between the hydraulic chambers and to block flow between the first fluid supply / discharge passage and the secondary hydraulic chamber via the fluid transfer / return passage And a selector valve operative to operate such that the pressure of the working fluid in the first fluid supply / discharge passage is controlled within the second fluid supply / discharge passage. The pressure of the working fluid in the second fluid supply / discharge passage is such that the pressure of the working fluid in the first fluid supply / discharge passage is determined when the first selector valve position is less than the pressure of the fluid. Is selected to determine the second selection valve position when the pressure of the working fluid in the first fluid supply / discharge passage is greater than the pressure of the working fluid in the second fluid supply / discharge passage. Operable to determine the third selector valve position, and the hydraulic system further comprises a brake resistance lister provided on the fluid transfer / return passage to restrict the flow of working fluid in the fluid transfer / return passage. Hydraulic systems are provided in accordance with another aspect of the present invention.

The features and advantages of the hydraulic system according to the invention will be more clearly understood from the following description taken with reference to the accompanying drawings.

Description of the Preferred Embodiments

Referring to FIGS. 1 to 5 of the accompanying drawings, a first preferred embodiment of the present invention will be described in detail later.

In FIG. 1, the hydraulic system embodying the present invention increases the working fluid by sucking the working fluid through the storage tank 56 containing the working fluid and the fluid suction passage 63 from the storage tank 56. It consists of a hydraulic pump 54 which carries with pressure. The hydraulic system is shown in FIG. 2 as including a cylindrical casing 12 and a valve casing 13, which are composed of a casing 11 fixedly attached to a frame member of a crawler vehicle, not shown, and tightly connected to each other. . The cylindrical casing 12 houses a cam plate type hydraulic motor 14 for driving a crawler vehicle. The camplate type hydraulic motor 14 is composed of an output rotating shaft 17 rotatably supported by a cylindrical casing 12 and a valve casing 13 via bearings 15 and 16. The output shaft 17 has one end projecting from the cylindrical casing 12 and fixedly connected to the sprocket held in engagement with the caterpillar, which is not shown.

The hydraulic motor 14 is shown in FIG. 1 as having first and second inlet / outlets 14a and 14b. The working fluid is supplied from the hydraulic pump 54 to one of the first and second inlet / outlets 14a, 14b through one of the first and second fluid supply / discharge passages 58, 59. And discharge to storage tank 56 from the other one of the first and second inlet / outlets 14a, 14b through the other one of the first and second fluid supply / discharge passages 58,59. do. The output shaft 17 of the hydraulic motor 14 is rotated in one direction when the working fluid from the hydraulic pump 54 is received by the first inlet / outlet 14a and the working fluid from the hydraulic pump 54 is removed. 2 is rotated in the opposite direction when received by the inlet / outlet 14b.

Referring to FIG. 2, reference numeral 20 denotes a cylinder block in which the other end of the rotary shaft 17 is received and the other end of the rotary shaft is connected by a spline connection. The cylinder blocks 20 are arranged in a circumferentially equidistant relationship with respect to each other and in parallel with the axis of rotation 17 from one end of the cylinder block 20 to the other end of the cylinder block. It is formed of a plurality of cylinder through bores 21 extending in the direction.

The cylinder block 20 has a plurality of protruding plungers 23 slidably received in each of the cylinder through bores 21, each protruding plunger 23 protrudes from one end of the cylinder block 20, respectively. It is formed as a ball-shaped portion 22 to be made.

Reference numeral 24 denotes a timing plate fixedly connected to the valve casing 13 and interposed between the cylinder block 20 and the valve casing 13. The timing plate 24 is formed of a pair of arcuate through bores 25 arranged symmetrically with respect to the axis of the cylinder block 20, each through bore being connected to the output shaft 17 with respect to the timing plate 20. As the cylinder block 21 rotates with respect to the cylinder through-bore 21 and in fluid communication with the non-fluid communication state alternately.

Between the other end of the cylinder block 20 and the cylindrical casing 12, a ring-shaped cam plate 28 through which the output rotation shaft passes is disposed. The cam plate 28 has an inclined surface 29 which is inclined with respect to an imaginary plane that intersects the output rotation shaft 17 of the hydraulic motor 14 at a right angle so that the cam plate 28 has an output rotation shaft of the hydraulic motor 14. The thin plate portion 30 and the thick plate portion 31 are divided by the virtual plane on which the rotation axis of 17 extends. The cam plate 28 is a first flat surface 33 parallel to the imaginary plane perpendicular to the output axis of rotation 17 and partially forming the surface of the thin plate powder 30 of the cam plate 28 and A further back 32 consisting of a second flat surface 34 which is inclined relative to the first flat surface 33 at a small angle of and partially forms the surface of the thick plate portion 31 of the camplate 28. Have. The cam plate 28 is pivotally fitted with respect to the lever member 35 disposed on the boundary between the first and second flat surfaces 33 and 34 so that the first flat surface 33 of the cam plate 28 can be adjusted. ) Is held in contact with the inner flat surface of the cylindrical casing 12 and the second flat surface 34 of the cam plate 28 is held in contact with the inner flat surface of the cylindrical casing 12. Determine two different camplate positions consisting of the second camplate position. The inclined surface 29 of the cam plate 28 is slidably engaged with a plurality of shoe members 38 such as the protruding plunger 23 in number, and each shoe member has a recess and each shoe The concave portion of the member 38 is connected to each protruding plunger 23 in such a way that it has a ball-shaped portion 22 of each protruding plunger 23 which is pivotally received.

The cylindrical casing 12 is open at the inner surface of the cylindrical casing 12 facing the first flat surface 33 of the cam plate 28 and the cylinder chamber 40 in which the pressure piston 14 is slidably received. ) Is formed. The cylindrical casing 12 is further formed with a speed variable fluid passage 42 provided with a restrictor 124 and held in fluid communication with the cylinder chamber 40.

When the high pressure working fluid is supplied to the cylinder chamber 40 through the speed variable fluid passage 42, the pressurizing piston 41 is protruded from the inner surface of the cylindrical casing 12 by the high pressure working fluid to form a cam plate ( 28) is moved from the first camplate position to the second camplate position. On the other hand, when the high pressure working fluid is blocked from being supplied to the cylinder chamber 40 through the speed variable fluid passage 42, the cam plate 28 is moved to determine the second plate position to the first plate position. Thus, the cam plate 28 movable to determine the first and second cam plate positions causes the protruding plunger 23 contained in the cylinder block 20 to move in the axial direction in different strokes, so that between different speed conditions. It is possible to change the rotational speed of the output shaft 17.

The speed variable fluid passage 42 may be connected to the control fluid passage 112 and the fluid outlet passage 101 through the speed control valve 113. Meshes with a control valve spool 120 slidably received by the valve casing 13 and one end of the control valve spool 120 and is supplied to the pilot hydraulic chamber 120a to supply the control valve spool 120. Consists of a helical spring 121 for moving the control valve spool 120 in the axial direction against the pilot pressure of the working fluid acting on the other end, the speed control valve 113 is shown in FIG. Is shown. The speed control valve 113 thus constructed is operated to determine two different control valve positions depending on the pilot pressure of the working fluid acting on the other end of the control valve spool 120. Referring back to FIG. 1, the control valve position of the speed control valve 113 may include a first control valve position G in which the speed variable fluid passage 42 is maintained in fluid communication with the control fluid passage 112. The speed variable fluid passage 42 is in the second control valve position I held in fluid communication with the fluid outflow passage 101.

The working fluid in the pilot hydraulic chamber 120a of the control spool valve 120 is supplied from the hydraulic pump 114 through the pilot fluid passage 119 and the fluid transfer passage 116. The pilot fluid passage 119 may be connected to the fluid discharge passage 123 as well as the fluid transfer passage 116 through the two-position directional control valve 117. The direction control valve 117 is operated to determine two different direction control valve positions according to manual operation by the crawler vehicle driver. The valve position of the two-position directional control valve 117 includes the first directional control valve position F and the pilot fluid passage 119 in which the pilot fluid passage 119 is in fluid communication with the fluid transfer passage 116. The second direction control valve position H is maintained in fluid communication with the fluid outlet passage 123. The hydraulic pump 114 sucks the working fluid from the storage tank 56 through the fluid suction passage 115 to pressurize the working fluid into the fluid transfer passage 116. A relief valve 122 is provided on the fluid transfer passage 116 such that the pressure of the working fluid in the fluid passage 116 does not exceed a predetermined pressure level.

Reference numeral 111 denotes a shuttle valve having a control fluid passage 112 which is in selective fluid communication with the first selective fluid passage 81 and the second selective fluid passage 82.

The first and second selective fluid passages 81 and 82 are the hydraulic motor side passage portion 58a of the first supply / discharge fluid passage 58 and the second supply / discharge fluid passage 59 to be described in detail below. Are maintained in fluid communication with the hydraulic motor side passage portion 59a. The working fluid in one of the first and second selective fluid passages 81, 82, which is in fluid communication with the control fluid passage 112, is the other of the first and second selective fluid passages 81, 82. It has a higher hydraulic pressure than the working fluid of one passage.

In FIG. 4, the member numbers 45 are arranged in a coaxial relationship spaced apart in the axial direction with respect to each other and a plurality of first friction rings fixedly connected to the outer circumferential surface portion of the cylinder block 20 of the hydraulic motor 14. The plate no. 46 represents a plurality of second friction ring plates fixedly connected to the inner circumferential surface portion of the cylindrical casing 12 and arranged alternately in coaxial relationship with the first friction ring plate 45. The first and second friction ring plates 45 and 46 form a friction plate assembly as a whole. The cylindrical casing 12 slidably receives the brake piston 47 positioned between the valve casing 13 and the friction plate assembly and surrounds the cylinder block 20. The brake piston 47 cooperates with the cylindrical casing 12 to form the main hydraulic chamber 48. A plurality of brake springs 49 are positioned between the brake piston 47 and the valve casing 13, and each brake spring presses the brake piston 47 to force the first friction ring plate 45 to the second friction ring. Push the plate 46 in order. If no high-pressure working fluid is supplied to the main hydraulic chamber 48, all of the brake springs 49 press the brake piston 47 to force the first friction ring plate 45 to the second friction ring plate 46. To push. This causes the first and second friction ring plates 45 and 46 to be engaged with each other by the elastic force of the brake spring 49 to generate a large friction force between the first and second friction ring plates 45 and 46. This results in the fact that the output shaft 17 is mechanically braked by the large friction force transmitted from the friction plate assembly through the cylinder block 20. When the high pressure working fluid is supplied to the main hydraulic chamber 48, the brake piston 47 is pressed by the working fluid pressure in the main hydraulic chamber 48 to move in the axial direction with respect to the elastic force of the brake spring 49. .

At this time, there is no friction force between the first and second friction ring plates 45 and 46, and as a result, not only the cylinder block 20 but also the output rotation shaft 17 is released from the mechanical braking force based on the brake spring 49. . The first and second friction ring plates 45 and 46, the brake piston 47 and the brake spring 49 work together to form a mechanical brake assembly 50.

The hydraulic system has a first and a second fluid supply / discharge passage 58, to have a fluid open passage 99 which is selectively in fluid communication with the first and second fluid supply / discharge passages 58, 59. It further comprises a shuttle valve 98 provided in (59). The working fluid in one of the first and second fluid supply / discharge passages 58, 59 which are in fluid communication with the fluid open passage 99 is provided with the first and second fluid supply / discharge passages 58, Higher pressure than the working fluid in the other passage.

The hydraulic system shown in FIG. 1 is further comprised of a control valve 100 provided in the fluid opening passage 99 and operable to determine two different control valve positions depending on the hydraulic pressure of the fluid opening passage 99. have. The control valve position of the control valve 100 is the first control valve position (D) and the working fluid is a fluid to flow the working fluid to the fluid opening passage 99 between the shuttle valve 98 and the main hydraulic chamber 48 The second control valve position E is discharged from the main hydraulic chamber 48 to the storage tank 56 through the outflow passage 101.

The hydraulic system is provided on the first and second fluid supply / discharge passages 58 and 59 to communicate with the hydraulic pump 54 and the storage tank 56 through the fluid transfer passage 55 and the fluid discharge passage 57 respectively. It is further configured as a direction control valve 53 in communication. The direction control valve 53 is operated to determine three different direction control valve positions according to manual operation by the crawler vehicle driver. The direction control valve position of the directional control valve 53 allows the working fluid to be supplied from the hydraulic pump 54 to the first fluid supply / discharge passage 58 via the fluid transfer passage 55 and the working fluid to the fluid discharge passage. A first directional control valve position (L) for discharging the second fluid supply / discharge passage (59) from the second fluid supply / discharge passage (59) to the storage tank (56), the working fluid being first and second through the fluid discharge passage (57). 2 The second directional control valve position (K) for discharging from the fluid supply / discharge passages (58, 59) to the storage tank (56), and the working fluid is discharged from the hydraulic pump (55) via the fluid transfer passage (55). 2 is a third directional control valve position J for supplying to the supply / discharge fluid passage 59 and for the working fluid to be discharged from the first fluid supply / discharge passage 58 via the fluid discharge passage 57. .

A relief valve 62 is provided on the fluid transfer passage 55 to prevent the pressure of the working fluid in the fluid transfer passage 55 from exceeding a predetermined pressure level.

The brake piston 47 and the cylindrical casing 12 further form a secondary hydraulic chamber 105 which is maintained in fluid communication with the fluid opening passage 99 via the fluid transfer / return passage 106.

A brake resistor lister 107 is provided on the fluid transfer / return passage 106 to limit the flow of the working fluid in the fluid transfer / return passage 106. The brake piston 47 is operated by the hydraulic pressure in the secondary hydraulic chamber 105 to disengage the brake piston 47 from the output shaft 17 of the hydraulic motor 14 against the elastic force of the brake spring 49. It further has a second piston area portion. The second piston area portion of the brake piston 47 has an effective area smaller than the effective area of the first piston area portion of the brake piston 47.

1 and 3, the hydraulic system is provided with a counterbalance valve provided on the first and second fluid supply / discharge passages 58, 59 between the hydraulic pump 14 and the directional control valve 53. 65). Under the condition that the directional control valve 53 is moved to determine the second directional control valve position K, the counterbalance valve 65 is operated with the hydraulic fluid 14 when the hydraulic motor 14 is still in operation. Is designed to prevent pressurization into one of the first and second fluid supply / discharge passages 58,59. More specifically, the hydraulic system includes a first check valve 90 provided on the first fluid supply / discharge passage 58 and a second check valve provided on a second fluid supply / discharge passage 59. It further consists of 91. The first fluid supply / discharge passage 58 is divided into a hydraulic motor side passage portion 58a and a directional control valve side passage portion 58b by a check valve 90. In a similar manner, the second fluid supply / discharge passage 59 is divided by the second check valve 91 into the hydraulic motor side passage portion 59a and the directional control valve side passage portion 59b. As shown in FIG. 3, the counterbalance valve 65 has inner ends 68a, 69a arranged in line with each other and facing each other and outer ends 68b, 69b spaced from each other, respectively. It consists of the 1st and 2nd valve spools 68,69. The first and second valve spools 68 and 69 are slidably received by the valve casing 13.

The inner ends 68a, 69a of the first and second valve spools 68, 69 and the valve casing 13 have a fluid transfer / return passage between the secondary hydraulic chamber 105 and the brake resistor restrictor 107. A central hydraulic chamber 76 which is in fluid communication with 106 is formed jointly. The outer end 68b of the first valve spool 68 cooperates with the valve casing 13 to maintain fluid communication with the passage portion 58a of the directional control valve side of the first fluid supply / discharge passage 58. One side hydraulic chamber 72 is formed.

Similarly, the outer end portion 69b of the second valve spool 69 cooperates with the valve casing 13 in fluid communication with the passage portion 59b of the direction control valve side of the second fluid supply / discharge passage 59. A second side hydraulic chamber 73 is formed.

The first valve spool 68 of the counterbalance valve 65 is a flow of the working fluid between the directional control valve side passage portion 58b of the first fluid supply / discharge passage 58 and the first side hydraulic chamber 72. Of the small diameter acting as a first restrictor 95 provided between the first side hydraulic chamber 72 and the passage portion 58a of the directional control valve side of the first fluid supply / discharge passage 58 to restrict the It is formed as a through bore.

The second spool 69 of the counterbalance valve 65 flows the working fluid between the passage portion 59b of the direction control valve side of the second fluid supply / discharge passage 59 and the second side hydraulic chamber 73. Small diameter through acting as a second restrictor 96 provided between the second side hydraulic chamber 73 and the passage control portion 59b of the direction control valve side of the second fluid supply / discharge passage 59 for the purpose of restriction. It is formed as a bore.

The counterbalance valve 65 is housed in the first and second side hydraulic chambers 72 and 73 and presses the first and second valve spools 68 and 69 to move inwards, respectively. It is further composed of return springs 74 and 75.

The first valve spool 68 of the counter balance valve 65 is moved in the axial direction such that the hydraulic fluid at the first spool position C moves the hydraulic motor side passage portion 58a of the first fluid supply / discharge passage 58. And a flow is allowed between the passage portion 58b of the directional control valve side of the first fluid supply / discharge passage 58 and in the second spool position A, the working fluid is connected to the first fluid supply / discharge passage 58. The flow is hindered between the hydraulic motor side passage portion 58a and the directional control valve side passage portion 58b of the first fluid supply / discharge passage 58.

The second valve spool 69 of the counterbalance valve 65 is moved in the axial direction such that the hydraulic fluid side passage portion 59a of the second fluid supply / discharge passage 59 moves the working fluid at the first spool position C. Flow is allowed between the passage portion 59b of the directional control valve side of the second fluid supply / discharge passage 59 and at the second spool position A, the working fluid is connected to the second fluid supply / discharge passage 59. Flow is obstructed between the hydraulic motor side passage portion 59a and the directional control valve side passage portion 59b of the second fluid supply / discharge passage 59.

When the first and second valve spools 68 and 69 are moved to the first spool position C, respectively, the working fluid is supplied to the hydraulic motor side of the first fluid supply / discharge passage 58 by the counter balance valve 65. It is further allowed to flow between the passage portion 58a and the motor side passage portion 59a of the second fluid supply / discharge passage 59. When the first and second valve spools 68 and 69 are moved to the second spool position A, respectively, the working fluid is supplied to the hydraulic motor side passage portion 58a and the second of the first fluid supply / discharge passage 58. The flow is disturbed between the hydraulic motor side passage portions 59a of the fluid supply / discharge passage 59.

Hydraulic pressure based on the pressure of the working fluid applied on the inner end 68a of the first valve spool 68 receives the pressure of the working fluid applied on the outer end 68b of the first valve spool 68. If greater than the sum of the hydraulic pressure based on the elastic force of the first return spring 74, the first valve spool 68 of the counterbalance valve 65 is moved to the first spool position (C). The hydraulic pressure based on the pressure of the working fluid applied on the inner end 68a of the first valve spool 68 and the hydraulic force of the working fluid applied on the outer end 68b of the first spool 68 If less than the sum of the elastic forces of the first return spring 74, the first valve spool 68 of the counterbalance valve 65 is moved to the second spool position A.

On the other hand, the hydraulic fluid based on the pressure of the working fluid applied on the inner end portion 69a of the second balance pull 69 receives the working fluid applied on the outer end portion 69b of the second valve spool 69. If the hydraulic pressure of the pressure based on the sum of the elastic force of the second return spring 75 is greater than the sum, the second valve spool 69 of the counterbalance valve 65 is moved to the first spool position C. The hydraulic pressure based on the pressure of the working fluid applied on the inner end of the second spool 69 is based on the pressure of the working fluid applied on the outer end 69b of the second valve spool 69. If less than the sum of the pressure and the elastic force of the second return spring 75, the second valve spool 69 of the counterbalance valve 65 is moved to the second spool position A.

As understood from FIG. 1, the first valve spool 68 of the counterbalance valve 65 is defined between the first spool position C and the second spool position A of the first valve spool 68. It has 3 spool position (B). Similarly, the second valve spool 69 of the counterbalance valve 65 has a third spool position B between the first spool position C and the second spool position A of the second valve spool 69. Has more.

When the first and second valve spools 68 and 69 are moved to the third spool position B, respectively, the working fluid is supplied to the hydraulic motor side passage portion 58a and the second of the first fluid supply / discharge passage 58. Flow is allowed between the hydraulic motor side passage portion 58a of the fluid supply / discharge passage 59.

And the operation of the hydraulic system will be described below. In order for the crawler vehicle to be driven by the hydraulic motor 14, the direction control valve 53 is switched to the first direction control valve position L or the third direction control valve position J. In this case, when the direction control valve 53 is switched to the third direction control valve position J, it will be described below. When the direction control valve 53 is switched to the third direction control valve position J, the high pressure working fluid is supplied from the hydraulic pump 54 to the second fluid supply / discharge passage 59.

As a result, the second fluid supply / discharge passage 59, the selection fluid passage 82, the fluid transfer / return passage 106, the fluid opening passage 99 and the control fluid passage 112 act as high pressure fluid passages. .

The high pressure working fluid is supplied from the hydraulic pump 54 to about half of the cylinder bore 21 through the fluid transfer passage 55, the second fluid supply / discharge passage 59, and the arcuate through bore 25, Therefore, the spherical portion of the protruding plunger 23 projects from the cylinder block 20 in turn and pushes the inclined surface 29 of the cam plate 28. The pushing plunger 23 and the shoe member 38 are pushed on the protruding plunger 23 to be moved from the thick plate portion 31 of the cam plate 28 toward the thin plate portion 30 of the cam plate 28. The force is applied by the components of the force, thereby rotating the output shaft 17 of the hydraulic motor 14 by the protruding plunger 23 and the cylinder block 20 to drive the crawler vehicle.

When the directional control valve 53 is in the third directional control valve position J as described above, the high pressure working fluid in the second fluid supply / discharge passage 59 is transferred to the fluid opening passage by the shuttle valve 98. Supplied to 99. The high pressure working fluid in the fluid opening passage 99 causes the control valve 100 to be in the first control valve position D and is supplied to the main hydraulic chamber 48 of the mechanical brake assembly 50.

At the same time, the high pressure working fluid of the fluid opening passage 99 is supplied to the secondary hydraulic chamber 105 of the mechanical brake assembly 50 via the fluid supply / discharge passage 106. The brake piston 47 of the mechanical brake assembly 50 is connected to the main hydraulic chamber 48 and the secondary hydraulic pressure by fluid pressure from the first and second friction ring plates 45 and 46 against the elastic force of the brake spring 49. Forced to disengage the quantum chamber 105, and consequently, the rotary shaft 17 of the hydraulic motor 14 is the friction force generated between the first and second friction ring plates (45, 46), that is, the brake spring ( Opening from the mechanical braking force generated by 49) causes the output shaft 17 of the hydraulic motor 14 to rotate freely.

The high pressure working fluid not only flows from the fluid transfer / return passage 106 to the central hydraulic chamber 76 of the counterbalance valve 65, but also from the fluid open passage 99 to the second side hydraulic chamber of the counter balance valve 65. Up to 73). This is derived from the fact that the second valve spool 69 of the counterbalance valve 65 is held in the second spool position A. On the other hand, the first side hydraulic chamber 72 of the counterbalance valve 65 maintains fluid communication with the first fluid supply / discharge passage 58 acting as the outflow passage, so that the first valve of the counterbalance valve 65 The spool 68 is moved to the first spool valve position C. FIG. The working fluid in the cylinder through bore 21 is the hydraulic motor side passage portion 58a of the first fluid supply / discharge passage 58, and the directional control valve side passage portion 58b of the first fluid supply / discharge passage 58. The fluid is discharged into the storage tank 56 through the fluid passage 81 and the fluid outlet passage 57.

If the hydraulic motor 14 is requested to be operated at high speed in order to have the small torque generated by it, the two-position directional control valve 117 is switched to the first directional control valve position F, where The working fluid is supplied from the hydraulic pump 114 to the pilot hydraulic chamber 120a of the speed control valve 113 through the pilot fluid passage 119. The speed control valve 113 is operated to the first speed control valve position G by the pilot oil pressure in the pilot hydraulic chamber 120a, so that the high pressure working fluid selected by the shuttle valve 111 is controlled fluid path 112. And through the variable speed fluid passage 42 is supplied to the cylinder chamber (40). The high pressure working fluid in the cylinder chamber 40 causes the pressure piston 41 to protrude from the inner surface of the cylindrical casing 12 so that the cam plate 28 is pivoted on the lever member 35 and moved to the second position. Here the second flat surface 34 of the camplate 28 is in contact with the inner surface of the cylindrical casing 12. This means that the protruding plunger 23 is reduced in stroke, and consequently, like the cylinder block 20, the output rotating shaft 17 is invariant in the amount of working fluid supplied from the hydraulic pump 54 to the hydraulic motor 14. Because of the fact that it rotates at high speed.

Conversely, if it is requested that the hydraulic motor 14 be operated at low speed in order to have the large torque generated by it, the two-position directional control valve 117 is switched to the second directional control valve position H, The working fluid is discharged from the pilot hydraulic chamber 120a of the control valve 113 to the storage tank 56 through the pilot fluid passage 119 and the fluid outlet passage 123. The speed control valve 113 is switched to the second speed control valve position I by the helical spring 121, where the working fluid of the cylinder chamber 40 is the speed variable fluid passage 42 and the fluid outlet passage 101. Is discharged into the storage tank (56). Therefore, the cam plate 28 is forced to pivot on the lever member 35 by the protruding plunger 23 so that the first flat surface 33 of the cam plate 28 is in contact with the inner surface of the cylindrical casing 12. The contact is switched to the first position.

This is because, as the stroke of the protruding plunger 23 increases, the cylinder block 20 as well as the output shaft 17 are rotated at low speed because the amount of the working fluid supplied from the hydraulic pump 14 to the hydraulic motor 14 does not change. Means that.

In order to stop the caterpillar vehicle, the direction control valve 53 is switched from the third direction control valve position (J) to the second direction control valve position (K), where the first and second fluids are supplied. The discharge passages 58 and 59 are in fluid communication with each other and serve as low pressure fluid passages.

In addition, since the fluid opening passage 98 also serves as a low pressure fluid passage, the supply of the high pressure working fluid to the main hydraulic chamber 48 of the mechanical brake 50 is stopped. At the same time, the control valve 100 is displaced to determine the second valve position E, in which the working fluid in the main hydraulic chamber 48 is discharged to the storage tank 56 via the fluid outlet passage 101. . As a result, the brake piston 47 of the mechanical brake assembly 50 is pressed by the brake spring 47 to engage the first and second friction ring plates 45 and 46, and the output shaft of the hydraulic motor 14 ( 17 is braked by the frictional force generated between the first and second friction ring plates 45 and 46. In the meantime, the working fluid in the secondary hydraulic chamber 105 passes the mechanical brake assembly through the fluid transfer / return passage 106, the first and second fluid supply / discharge passages 58 and 59, and the fluid outlet passage 57. According to the movement of the brake piston 47 of the 50, it is discharged to the storage tank 56. The fluid pressure in the main hydraulic chamber 48 immediately decreases to the low pressure level of the storage tank 56 for a short time between the points T1 and T2 shown in FIG. 5, while the fluid pressure in the secondary hydraulic chamber 105 is reversed. For a short time between the points T1 and T2, the pressure gradually decreases to a predetermined pressure level higher than the low pressure level of the storage tank 56, which is provided with a brake resistor restrictor 107 on the transfer / return passage 106 to provide fluid. This is because the working fluid flow in the transfer / return passage 106 is restricted.

That is, the fluid pressure in the secondary hydraulic chamber 105 which is less than the delivery pressure of the hydraulic pump 54 and gradually decreases acts on the second piston area portion of the brake piston 47 of the mechanical brake assembly 50. It is adapted to prevent the brake piston 47 from immediately engaging the first and second friction ring plates 45 and 46.

After the brake piston 47 of the mechanical brake assembly 50 begins to move toward the first and second friction ring plates 45 and 46, the first friction ring plate 45 rotates at the point T2 to thereby rotate the second friction ring. Engaging with the plate 46, thereby applying the mechanical braking force of the mechanical brake (50) to the output rotary shaft 17 of the hydraulic motor (14). Since a part of the elastic force of the brake spring is dissipated by the fluid pressure in the secondary hydraulic chamber 105, the mechanical braking force based on the elastic force of the brake spring 49 and the fluid pressure in the secondary hydraulic chamber 105 is determined by the brake spring 49. This is considerably smaller compared to the case based only on. Therefore, since the rotation speed of the rotary shaft 17 of the hydraulic motor 14, that is, the drive speed of the endless tracked vehicle, gradually decreases with a deceleration indicated by 0.4 g or less, the endless tracked vehicle is decelerated and a strong shock occurs when it stops. Can be effectively prevented.

Moreover, the fluid pressure in the secondary hydraulic chamber 105 of the mechanical brake assembly 50 is maintained at a constant low pressure level during the time between T2 and T3 points, as can be seen from FIG. 5, and the reason is as follows. During the time between the T2 and T3 points, the second valve spool 69 of the counterbalance valve 65 moves from the second spool position A toward the first spool position C through the brake resistor listr 107. The working fluid equal to the amount discharged consequently continues from the central hydraulic chamber 76 of the counterbalance valve 65 to the fluid transfer / return passage 106 between the secondary hydraulic chamber 105 and the brake resistance restrictor 107. This is because it is supplied. The fluid pressure in the fluid transfer / return fluid passage 106 between the secondary hydraulic chamber 105 as well as the secondary hydraulic chamber 105 and the brake resistance restrictor 107 is maintained at a constant low pressure level.

Therefore, the mechanical braking force exerted on the output shaft 17 of the hydraulic motor 14 by the mechanical brake assembly 50 is maintained at a constant small level of force for a certain period of time, so that a strong impact when the crawler vehicle is decelerated and stopped. Generation can be prevented more effectively.

The rotation of the output shaft 17 of the hydraulic motor 14 moves the direction control valve 53 from the third direction control valve position J to the second direction control valve position K while the endless track vehicle travels at high speed. By switching, the output shaft 17 can be stopped before the point T3 when the speed decreases.

In this case, the hydraulic motor 14 serves as a hydraulic pump. However, the first valve spool 68 of the counterbalance valve 65 is returned from the third spool position B to the second spool position A, in the direction of the first fluid supply / discharge passage 58 at point T3. The hydraulic motor side passage portion 58a of the first fluid supply / discharge passage 58 is separated from the control valve side passage portion 58b, so that the hydraulic motor side of the first fluid supply / discharge passage 58 is separated. The passage portion 58a is increased in pressure to apply a fluid braking force to the hydraulic motor 14. Therefore, the output shaft 17 of the hydraulic motor 14 is braked and stopped by both the mechanical braking force generated by the mechanical brake assembly 50 and the fluid braking force based on the operation of the counterbalance valve 65. The braking force exerted on the hydraulic motor 14 by the mechanical brake assembly 50 after T3 is based only on the mechanical braking force and consequently based on the mechanical braking force partially dissipated by the fluid pressure in the secondary hydraulic chamber 105. This is greater than that because the fluid pressure in the secondary hydraulic chamber 105 decreases to the low pressure level of the storage tank 56. The mechanical braking force based on the static frictional force generated between the first and second friction ring plates 45 and 46 when the hydraulic motor 14 completely stops at the point T4 shown in FIG. 5 is the output of the hydraulic motor 14. Is applied to the rotary shaft 17. When the hydraulic motor 14 is completely stopped before the point T3, no fluid braking force is applied to the hydraulic motor 14.

When the direction control valve 53 is switched from, for example, the third direction control valve position J to the first direction control valve position L via the second direction control valve position K, the output shaft of the hydraulic motor 14 is rotated. (17) continues to rotate in the same direction for a very short time. At this time, the hydraulic motor 14 sucks the working fluid from the second fluid supply / discharge passage 59 serving as the low pressure passage and operates as the first fluid supply / discharge fluid passage 58 serving as the high pressure passage. The fluid is pressurized. However, the working fluid in the first side hydraulic chamber 72 of the counterbalance valve 65 increases the pressure to a high pressure level equal to the fluid pressure of the first fluid supply / discharge passage 58 while the counterbalance valve 65 The working fluid in the second side hydraulic chamber 73 of the pressure decreases to the low pressure level of the storage tank 56. The first valve spool 68 of the counterbalance valve 65 moves from the first spool position C to the second spool position A while the second valve spool 69 of the counterbalance valve 65 2 It is moved from the spool position A to the first spool position C.

During the movement of the first and second valve spools 68 and 69, the fluid pressure in the central hydraulic chamber 76 between the first and second valve spools 68 and 69 is maintained at a high pressure level so that the working fluid is completely countered. It is not supplied to or discharged from the central hydraulic chamber 76 of the balance valve 65.

Since the first and second valve spools 68 and 69 are axially moved at the same speed in an invariant positional relationship with each other, the first and second valve spools 68 and 69 are connected to the first selective fluid passage 81. Through the passage 83, the third spool position B in fluid communication with the second selective fluid passage is simultaneously determined. The high pressure working fluid is therefore discharged from the first fluid supply / discharge passage 58 into the second fluid supply / discharge passage 59 containing the low pressure working fluid therein and within the first fluid supply / discharge passage 58. Surge pressure is prevented from occurring and cavitation is prevented from occurring in the second fluid supply / discharge passage 59.

Although the first and second valve spools 68 and 69 of the counterbalance valve 65 are formed by different components, respectively, the first and second valve spools 68 and 69 may be integrally formed with each other. It may be. In this case, a pair of hydraulic chambers replacing the central hydraulic chamber 76 may be formed in cooperation with the valve casing by each of one end and the other end of the spool body jointly formed by the first and second spools. have. The central hydraulic chamber 76 of the counter balance valve 65 is kept in fluid communication with the fluid transfer / return passage 106 to supply the working fluid contained in the central hydraulic chamber 76 in the fluid transfer / return passage 106. Although intended to be replenished, the central hydraulic chamber 76 may be separated into a fluid transfer / return passage 106. In this case the fluid pressure in the secondary hydraulic chamber 105 of the mechanical brake assembly 50 is reduced relatively quickly to the low pressure level of the storage tank 56.

6 shows a second preferred embodiment of the hydraulic system according to the invention. The second embodiment shown is a variation of the first embodiment shown in FIGS. 1-5, and includes a hydraulic motor 14, a hydraulic mechanical brake assembly 50, a control valve 100, and a speed control valve 113. , Shuttle valve 111, first check valve 90, second check valve 91, counterbalance valve 65, shuttle valve 98, directional control valve 53, relief valve 62, hydraulic pressure It consists of a pump 54, a two-position directional control valve 117, a hydraulic pump 54, a relief valve 122, and a storage tank 56, these components are the first of Figs. It is exactly the same as each corresponding element of the embodiment. The hydraulic system shown in FIG. 6 differs from the first embodiment of FIGS. 1 to 5 only in the hydraulic circuit which is kept in fluid communication with the secondary hydraulic chamber 105 only. The only difference between the examples will be explained later to avoid repetition.

In FIG. 6, the secondary hydraulic chamber 105 of the mechanical brake assembly 50 is connected to the storage tank 56 through the fluid transfer / return passage 156 which is maintained in fluid communication with the fluid outlet passage 101. It is in fluid communication. A brake resistor restrictor 157 is provided on the fluid transfer / return passage 156 to restrict the flow of the working fluid in the fluid transfer / return passage 156.

The fluid outlet passage 101 is provided with a check valve 159 to allow the working fluid to flow only from the storage tank to the secondary hydraulic chamber 105 through the fluid outlet passage 101 and another fluid transfer / return passage 158. Another fluid transfer / return passage 158 is maintained in fluid communication with the fluid transfer / return passage 156 between the brake resistance restrictor 157 and the secondary hydraulic chamber 105. For the same reason as described in the above-described first embodiment shown in FIGS. 1 to 5, the hydraulic system shown in FIG. 6 can effectively prevent the occurrence of a strong shock when the crawler vehicle is decelerated and stopped. Has the advantage that it can. It should be noted that the secondary hydraulic chamber 105 of the mechanical brake assembly 50 does not remain in fluid communication with the fluid open passage 99.

During the braking operation of the mechanical brake assembly 50, no hydraulic fluid is supplied to the fluid transfer / return passage 156 between the secondary hydraulic chamber 105 and the brake resistance restrictor 157, so that the hydraulic pressure shown in FIG. The system implements the first embodiment shown in FIGS. 1-5 in that the fluid pressure in the secondary hydraulic chamber 105 of the mechanical brake assembly 50 is reduced relatively quickly to the low pressure level of the storage tank 56. It is different from yes.

7 to 8 show a third preferred embodiment of the hydraulic system according to the invention. The third embodiment shown is a variation of the first embodiment shown in FIGS. 1 to 5 and is a hydraulic motor 14, a hydraulic mechanical brake assembly 50, a control valve 100, a speed control valve 113. , Shuttle valve 111, first check valve 90, second check valve 91, counterbalance valve 65, shuttle valve 98, directional control valve 53, relief valve 62, hydraulic pressure It consists of a pump 54, a two-position directional control valve 117, a hydraulic pump 54, a relief valve 122 and a storage tank 56, these components of the first embodiment of Figs. It is exactly the same as each corresponding element of the example. The hydraulic system shown in FIG. 7 differs from the first embodiment of FIGS. 1 to 5 only in the hydraulic circuit which is kept in fluid communication with the secondary hydraulic chamber 105 and the first and third embodiments. The only difference between them will be explained later to avoid repetition.

In FIG. 7 a selector valve 173 is provided on the first and second fluid supply / discharge passages 58 and 59. The selector valve 173 operates to determine three different selector valve positions according to the pressure difference between the working fluid in the first fluid supply / discharge passage 58 and the working fluid in the second supply / discharge passage 59. . The selector valve position allows the working fluid to flow between the first fluid supply / discharge passage 58 and the secondary hydraulic chamber 105 via the fluid transfer / return passage 176 to open the fluid transfer / return passage 136. First selection valve position (P) at which the flow between the second fluid supply / discharge passage 59 and the secondary hydraulic chamber 105 is blocked, the first working fluid via the fluid transfer / return passage 136 Second selection valve position (Q) at which flow is interrupted between the fluid supply / discharge passage 58 and the secondary hydraulic chamber 105 and between the second fluid supply / discharge passage 59 and the secondary hydraulic chamber 105. ) And the working fluid can flow between the second fluid supply / discharge passage 59 and the secondary hydraulic chamber 105 through the fluid transfer / return passage 136 to remove the fluid through the fluid transfer / return passage 136. It consists of the 3rd selection valve position R which interrupts | flows between the 1st fluid supply / discharge passage 58 and the secondary hydraulic chamber 105. FIG.

The selector valve 173 operates to determine the first selector valve position P when the pressure of the working fluid in the first fluid supply / discharge passage 58 is less than the working fluid pressure in the first supply / discharge passage 59. do.

When the pressure of the working fluid in the first fluid supply / discharge passage 58 is equal to the working fluid pressure in the second fluid supply / discharge passage 59, the selector valve 173 determines the second selector valve position Q. To work.

The selector valve 173 operates to determine the third selector valve position R when the pressure of the working fluid in the first fluid supply / discharge passage 58 is greater than the working fluid pressure of the second fluid supply / discharge passage 59. do.

A brake resistor restrictor 177 is provided on the fluid transfer / return passage 136 to restrict the working fluid flow in the fluid transfer / return passage 176. The selector valve 173 is shown in FIG. 8 and includes a cylindrical member 178 having a cylinder bore 178, a valve spool 179 slidably received by the cylindrical member 178, and a sealed cylinder bore ( It is composed of a plug member 180 having an opening of 178a. The cylindrical member 178 includes a first fluid port 178b having a cylinder bore 178a in fluid communication with the first fluid supply / discharge passage 58, and a second fluid supply / discharge passage 58. A second fluid port 178c having a cylinder bore 178a in fluid communication and a third fluid port having a cylinder bore 178a in fluid communication with the fluid transfer / return passage 176 ( 178d) is further formed. When the valve spool 179 is in contact with the right side wall of the cylinder member 178 in FIG. 8, the selector valve 173 has the fluid transfer / return passage 176 connected to the third fluid port 178d of the selector valve 173. And the first selection valve position P, which remains in fluid communication with the first fluid supply / discharge fluid passage 58 via the cylindrical bore 178a and the first fluid port 178b. When the valve spool 179 is located in the longitudinal center of the cylinder bore 178a, the selector valve 173 has a fluid transfer / return passage 176 with the first and second fluid supply / discharge passages 58 and 59. The second selector valve position Q, which is kept separated, is determined. When the valve spool 179 is brought into contact with the plug member 180, the selector valve 173 has a fluid transfer / return passage 176 such that the third fluid port 178d and the cylinder bore 178a of the selector valve 173 are provided. And a third selection valve position R which is maintained in fluid communication with the second fluid supply / discharge passage 59 via the second fluid port 178c. The hydraulic system shown in FIGS. 7 and 8 for the same reason as described in the above-described first embodiment shown in FIGS. 1 to 5 generates a strong shock when the crawler vehicle is decelerated and stopped. This has the advantage that it can be effectively prevented.

The foregoing description is of the preferred embodiment of the present invention, in which various changes and modifications can be made in accordance with the appended claims without departing from the spirit and scope of the invention. If you grow up, you will understand.

1 is a schematic view showing a first preferred embodiment of a hydraulic system according to the invention,

FIG. 2 is a sectional view showing a hydraulic device partially applied to the hydraulic system shown in FIG. 1;

3 is a cross-sectional view showing the counter balance valve shown in FIG.

4 is a partially enlarged cross-sectional view showing the mechanical brake assembly and the hydraulic motor shown in FIG.

FIG. 5 shows the variation of the hydraulic pressure in the main hydraulic chamber of the secondary hydraulic chamber of the mechanical brake assembly, the variation of the hydraulic pressure in the lower fluid supply / discharge passage shown in FIG. 1, and the total braking force applied to the output shaft of the hydraulic motor. Diagram showing variation,

FIG. 6 is a schematic view similar to FIG. 1 but showing a second preferred embodiment of a hydraulic system according to the invention;

7 is a schematic view similar to FIG. 1 but showing a third preferred embodiment of a hydraulic system according to the invention,

8 is a cross-sectional view showing the selector valve shown in FIG.

9 is a schematic view showing a conventional hydraulic system.

Explanation of symbols on the main parts of the drawings

12 cylindrical cylinder 14 hydraulic motor 17 output shaft

47: brake piston 48: main hydraulic chamber 49: brake spring

50: mechanical brake assembly 53: directional control valve

98: shuttle valve 99: fluid opening passage 106: fluid transfer / return passage

Claims (14)

In the hydraulic system, A storage tank for storing working fluid; A hydraulic pump for sucking the working fluid from the storage tank to discharge the working fluid by increasing the pressure; It has a first and a second inlet / outlet and an output shaft, the working fluid is supplied from the hydraulic pump to one of the first and second inlet / outlet through one of the first and second fluid supply / discharge passage And discharge from the other of the first and second inlet / outlets to the storage tank through the other of the first and second fluid supply / discharge passages, and the output rotating shaft is a working fluid from the hydraulic pump. A hydraulic motor which rotates in one direction when the first inlet / outlet is received and the output shaft rotates in the opposite direction when the working fluid from the hydraulic pump is received by the second inlet / outlet; And a brake piston engageable with the output rotation shaft of the hydraulic motor, wherein the cylindrical casing has a brake spring for elastically pressing the brake piston to engage the output piston of the hydraulic motor and the brake piston that is slidably received. And the brake piston and the cylindrical casing jointly form a main hydraulic chamber through which a working fluid is supplied through the fluid opening passage, and the working fluid is discharged through the fluid opening passage, and the brake piston is formed within the main hydraulic chamber. A pressure portion of the working fluid has a first piston area portion applied to disengage the brake piston from the output shaft of the hydraulic motor with respect to the elastic force of the brake spring, the output shaft of the hydraulic motor being hydraulic oil Is mechanically braked by the elastic force of the brake spring through the brake piston when the pressure is released from the main hydraulic chamber of the mechanical brake assembly, and the output shaft of the hydraulic motor has a working fluid in the main hydraulic chamber of the mechanical brake assembly. A mechanical brake assembly adapted to be released from the brake piston by a fluid pressure of a working fluid in the main hydraulic chamber when supplied to the main hydraulic chamber; Provided on the first and second fluid supply / discharge passages to have the fluid open passage selectively maintained in fluid communication with the first and second fluid supply / discharge passages, and in fluid communication with the fluid open passage. A working valve in one of the first and second fluid supply / discharge passages maintained in a state may have a higher pressure than a working fluid in the other of the first and second fluid supply / discharge passages; It is provided on the first and second fluid supply / discharge passage, the working fluid is supplied from the hydraulic pump to the first fluid supply / discharge passage and from the second fluid supply / discharge passage to the storage tank A first directional control valve position to be discharged, a second directional control valve position to allow the working fluid to be discharged from the first and second fluid supply / discharge passages to the storage tank, and a working fluid to the A directional control valve operative to determine three different directional control valve positions consisting of a third directional control valve position adapted to be supplied to a second fluid supply / discharge passage and to be discharged from the first fluid supply / discharge passage; And The hydraulic motor is provided on the first and second fluid supply / discharge passages between the hydraulic pump and the directional control valve, and the hydraulic motor is operated while the directional control valve is displaced to determine the second directional control valve position. A counterbalance valve operative to prevent pressurization of the working fluid by the hydraulic motor during one of the first and second fluid supply / discharge passages; It consists of The brake piston and the cylindrical casing further form a secondary hydraulic chamber maintained in fluid communication with the fluid opening passage through a fluid transfer / return passage, wherein the brake piston has a pressure of the working fluid in the secondary hydraulic chamber. Has a second piston area portion applied against the elastic force of the brake spring, And the hydraulic system further comprises a brake resistor restrictor provided on the fluid transfer / return passage to limit the flow of working fluid in the fluid transfer / return passage. 2. The hydraulic system according to claim 1, wherein the first piston area portion of the brake piston has a larger effective area than the second piston area portion of the brake piston. The first control valve position and the working fluid of claim 1, wherein the first control valve position and the working fluid are provided on the fluid opening passage, and a working fluid flows through the fluid opening passage between the shuttle valve and the main hydraulic chamber. And a control valve operative to determine two different control valve positions consisting of second control valve positions adapted to be discharged from said main hydraulic chamber to said storage tank via an open passage. The first check valve provided on the first fluid supply / discharge passage, and a working fluid to allow the working fluid to flow only from the direction control valve to the first inlet / outlet of the hydraulic motor. A second check valve provided on the second fluid supply / discharge passage to flow only from the direction control valve to the second inlet / outlet of the hydraulic motor, The first fluid supply / discharge passage is separated by the first check valve into a hydraulic motor side passage portion and a directional control valve side passage portion, and the second fluid supply / discharge passage is a hydraulic motor side passage portion and a direction control valve. Separated by the second check valve into the side passage portion, The counterbalance valve includes first and second valve spools arranged in alignment with each other and each having an inner end facing each other and an outer end remote from each other, A valve casing has said first and second valve spools slidably received, wherein an inner end of said first and second valve spools and said valve casing comprise said fluid between said secondary hydraulic chamber and said resistance restrictor. A central hydraulic chamber which is maintained in fluid communication with the transfer / return passage is jointly formed, and the outer end of the first valve spool and the valve casing are connected to the passage control valve side passage portion of the first fluid supply / discharge passage. A first side hydraulic chamber maintained in fluid communication is formed jointly, and the outer end of the second valve spool and the valve casing are in fluid communication with the passage control valve side passage portion of the second fluid supply / discharge passage. Jointly forming a second side hydraulic chamber maintained at A first return spring pressurizes the first valve spool to move toward the second valve spool, A second return spring pressurizes the second valve spool to move toward the first valve spool, The first restrictor is adapted to restrict the flow of the working fluid between the first side hydraulic chamber and the passage control valve side passage portion of the first fluid supply / discharge passage. It is provided between the passage part and the directional control valve side of the supply / discharge passage, The second restrictor is adapted to restrict the flow of working fluid between the second side hydraulic chamber and the passage control valve side passage portion of the second fluid supply / discharge passage. It is provided between the passage part and the passage control valve side of the supply / discharge passage, The first valve spool of the counterbalance valve allows a working fluid to flow between the hydraulic motor side passage portion of the first fluid supply / discharge passage and the directional control valve side passage portion of the first fluid supply / discharge passage. Spool where the first spool position and the working fluid are blocked from flow between the hydraulic motor side passage portion of the first fluid supply / discharge passage and the directional control valve side passage portion of the first fluid supply / discharge passage Axially movable to determine two different spool positions of position, The second valve spool of the counterbalance valve allows a working fluid to flow between the hydraulic motor side passage portion of the second fluid supply / discharge passage and the directional control valve side passage portion of the second fluid supply / discharge passage. Spool where the first spool position and the working fluid are blocked between the hydraulic motor side passage portion of the second fluid supply / discharge passage and the directional control valve side passage portion of the second fluid supply / discharge passage Axially movable to determine two different spool positions of position, The working fluid is the hydraulic motor side passage portion of the first fluid supply / discharge passage and the hydraulic motor side passage of the second fluid supply / discharge passage when the first and second valve spools are respectively moved to determine the first spool position. Between the part and the counterbalance valve, and the working fluid is the hydraulic motor side passage of the first fluid supply / discharge passage when the first and second valve spools are moved to determine the second spool position, respectively. The flow is blocked by the counterbalance valve between the portion and the hydraulic motor side passage portion of the second fluid supply / discharge passage, The first valve spool of the counterbalance valve has hydraulic pressure of the working fluid applied to the inner end of the first valve spool and the hydraulic pressure of the working fluid applied to the outer end of the first valve spool and the first return spring. The first valve spool of the counterbalance valve is the hydraulic force of the working fluid applied to the inner end of the first valve spool when the first spool position is greater than the sum of the elastic force of the first spool Is moved to determine the second spool position when less than the sum of the hydraulic force of the working fluid applied to the outer end of the first spring and the elastic force of the first return spring, The second valve spool of the counterbalance valve has hydraulic pressure of the working fluid applied to the inner end of the second valve spool and the hydraulic pressure of the working fluid applied to the outer end of the second valve spool and the second return spring. The second valve spool of the counterbalance valve is moved to determine the second spool position when the elastic force of the second spool is greater than the sum of the elastic force of the second valve spool. And the hydraulic system is moved to determine the second spool position when less than the sum of the hydraulic force of the working fluid applied to the outer end of the spool and the elastic force of the second return spring. The counterbalance valve of claim 4, wherein the first valve spool of the counter balance valve further determines a third spool position between a first spool position and a second spool position of the first valve spool, Wherein the second valve spool further determines a third spool position between a first spool position and a second spool position of the second valve spool, and a working fluid is such that the first and second valve spools are respectively The hydraulic pressure flows between the hydraulic motor side passage portion of the first fluid supply / discharge passage and the hydraulic motor side passage portion of the second fluid supply / discharge passage when moved to determine the third spool position. system. In the hydraulic system, A storage tank for storing working fluid; A hydraulic pump for sucking the working fluid from the storage tank to discharge the working fluid by increasing the pressure; It has a first and a second inlet / outlet and an output shaft, the working fluid is supplied from the hydraulic pump to one of the first and second inlet / outlet through one of the first and second fluid supply / discharge passage And discharge from the other of the first and second inlet / outlets to the storage tank through the other of the first and second fluid supply / discharge passages, and the output rotating shaft is a working fluid from the hydraulic pump. A hydraulic motor which rotates in one direction when the first inlet / outlet is received and the output shaft rotates in the opposite direction when the working fluid from the hydraulic pump is received by the second inlet / outlet; And a brake piston engageable with the output rotation shaft of the hydraulic motor, wherein the cylindrical casing has a brake spring for elastically pressing the brake piston to engage the output piston of the hydraulic motor and the brake piston that is slidably received. And the brake piston and the cylindrical casing jointly form a main hydraulic chamber through which a working fluid is supplied through the fluid opening passage, and the working fluid is discharged through the fluid opening passage, wherein the brake piston is located within the main hydraulic chamber. A pressure portion of the working fluid has a first piston area portion applied to disengage the brake piston from the output shaft of the hydraulic motor with respect to the elastic force of the brake spring, the output shaft of the hydraulic motor being hydraulic oil Is mechanically braked by the elastic force of the brake spring through the brake piston when the pressure is released from the main hydraulic chamber of the mechanical brake assembly, and the output shaft of the hydraulic motor has a working fluid in the main hydraulic chamber of the mechanical brake assembly. A mechanical brake assembly adapted to be released from the brake piston by fluid pressure in the main hydraulic chamber when supplied to the main hydraulic chamber; Provided on the first and second fluid supply / discharge passages to have the fluid open passage selectively maintained in fluid communication with the first and second fluid supply / discharge passages, and in fluid communication with the fluid open passage. A working valve in one of the first and second fluid supply / discharge passages maintained in a state may have a higher pressure than a working fluid in the other of the first and second fluid supply / discharge passages; It is provided on the first and second fluid supply / discharge passage, the working fluid is supplied from the hydraulic pump to the first fluid supply / discharge passage and from the second fluid supply / discharge passage to the storage tank A first directional control valve position to be discharged, a second directional control valve position to allow the working fluid to be discharged from the first and second fluid supply / discharge passages to the storage tank, and a working fluid to the A directional control valve operative to determine three different directional control valve positions consisting of a third directional control valve position adapted to be supplied to a second fluid supply / discharge passage and to be discharged from the first fluid supply / discharge passage; And The hydraulic motor is provided on the first and second fluid supply / discharge passages between the hydraulic pump and the directional control valve, and the hydraulic motor is operated while the directional control valve is displaced to determine the second directional control valve position. A counterbalance valve operative to prevent pressurization of the working fluid by the hydraulic motor during one of the first and second fluid supply / discharge passages; It consists of The brake piston and the cylindrical casing further form a secondary hydraulic chamber maintained in fluid communication with the storage tank through a fluid transfer / return passage, wherein the brake piston has a pressure of the working fluid in the secondary hydraulic chamber. Has a second piston area that is applied against the elastic force of the brake spring, And the hydraulic system further comprises a brake resistor restrictor provided on the fluid transfer / return passage to limit the flow of working fluid in the fluid transfer / return passage. 7. The secondary hydraulic chamber of claim 6, wherein the secondary hydraulic chamber is maintained in fluid communication with the storage tank via another fluid transfer / return passage and wherein the hydraulic system is such that a working fluid is transferred from the storage tank to the secondary hydraulic chamber only. And a check valve provided on said another fluid transfer / return passage to flow. 7. The first control valve position and the working fluid according to claim 6, wherein the first control valve position and the working fluid are provided on the fluid opening passage, and a working fluid flows through the fluid opening passage between the shuttle valve and the main hydraulic chamber. And a control valve operative to determine two different control valve positions comprising a second control valve position to be discharged from said main hydraulic chamber to said storage tank through an open passage. 7. The valve according to claim 6, wherein the first check valve provided on the first fluid supply / discharge passage and the working fluid are provided so that the working fluid flows only from the directional control valve to the first inlet / outlet of the hydraulic motor. A second check valve provided on the second fluid supply / discharge passage to flow only from the direction control valve to the second inlet / outlet of the hydraulic motor, The first fluid supply / discharge passage is separated by the first check valve into a hydraulic motor side passage portion and a directional control valve side passage portion, and the second fluid supply / discharge passage is a hydraulic motor side passage portion and a direction control valve. Separated by the second check valve into the side passage portion, The counterbalance valve includes first and second valve spools arranged in alignment with each other and each having an inner end facing each other and an outer end remote from each other, The valve casing has the first and second valve spools slidably received, the inner end of the first and second valve spools and the valve casing are in a central hydraulic chamber maintained in fluid communication with the fluid opening passage. And the outer end portion of the first valve spool and the valve casing jointly form a first side hydraulic chamber maintained in fluid communication with a passage portion of the directional control valve side of the first fluid supply / discharge passage. And the outer end of the second valve spool and the valve casing jointly form a second side hydraulic chamber maintained in fluid communication with a passage portion of the directional control valve side of the second fluid supply / discharge passage, A first return spring pressurizes the first valve spool to move toward the second valve spool, A second return spring pressurizes the second valve spool to move toward the first valve spool, The first restrictor is adapted to restrict the flow of the working fluid between the first side hydraulic chamber and the passage control valve side passage portion of the first fluid supply / discharge passage. It is provided between the passage part and the directional control valve side of the supply / discharge passage, The second restrictor is adapted to restrict the flow of working fluid between the second side hydraulic chamber and the passage control valve side passage portion of the second fluid supply / discharge passage. It is provided between the passage part and the directional control valve side of the supply / discharge passage, A third restrictor is provided between the central hydraulic chamber and the fluid opening passage to restrict the flow of working fluid between the central hydraulic chamber of the counterbalance valve and the fluid opening passage, The first valve spool of the counterbalance valve allows a working fluid to flow between the hydraulic motor side passage portion of the first fluid supply / discharge passage and the directional control valve side passage portion of the first fluid supply / discharge passage. Spool where the first spool position and the working fluid are blocked from flow between the hydraulic motor side passage portion of the first fluid supply / discharge passage and the directional control valve side passage portion of the first fluid supply / discharge passage Axially movable to determine two different spool positions of position, The second valve spool of the counterbalance valve allows a working fluid to flow between the hydraulic motor side passage portion of the second fluid supply / discharge passage and the directional control valve side passage portion of the second fluid supply / discharge passage. Spool where the first spool position and the working fluid are blocked from flow between the hydraulic motor side passage portion of the second fluid supply / discharge passage and the directional control valve side passage portion of the second fluid supply / discharge passage Axially movable to determine two different spool positions of position, The working fluid is the hydraulic motor side passage portion of the first fluid supply / discharge passage and the hydraulic motor side passage of the second fluid supply / discharge passage when the first and second valve spools are respectively moved to determine the first spool position. Between the part and the counterbalance valve, and the working fluid is the hydraulic motor side passage of the first fluid supply / discharge passage when the first and second valve spools are moved to determine the second spool position, respectively. Between the portion and the hydraulic motor side passage portion of the second fluid supply / discharge passage is blocked by the counterbalance valve, The first valve spool of the counterbalance valve has hydraulic pressure of the working fluid applied to the inner end of the first valve spool and the hydraulic pressure of the working fluid applied to the outer end of the first valve spool and the first return spring. The first valve spool of the counterbalance valve is the hydraulic force of the working fluid applied to the inner end of the first valve spool when the first spool position is greater than the sum of the elastic force of the first spool Is moved to determine the second spool position when less than the sum of the hydraulic force of the working fluid applied to the outer end of the first spring and the elastic force of the first return spring, The second valve spool of the counterbalance valve has hydraulic pressure of the working fluid applied to the inner end of the second valve spool and the hydraulic pressure of the working fluid applied to the outer end of the second valve spool and the second return spring. The second valve spool of the counterbalance valve is moved to determine the second spool position when the elastic force of the second spool is greater than the sum of the elastic forces of the hydraulic fluid applied to the inner end of the second valve spool. And the hydraulic pressure of the working fluid applied to the outer end of the hydraulic system is smaller than the sum of the elastic force of the second return spring to determine the second spool position. 10. The method of claim 9, wherein the first valve spool of the counterbalance valve further determines a third spool position between a first spool position and a second spool position of the first valve spool, and the counterbalance valve Wherein the second valve spool further determines a third spool position between a first spool position and a second spool position of the second valve spool, and a working fluid is such that the first and second valve spools are respectively The hydraulic pressure flows between the hydraulic motor side passage portion of the first fluid supply / discharge passage and the hydraulic motor side passage portion of the second fluid supply / discharge passage when moved to determine the third spool position. system. In the hydraulic system, A storage tank for storing working fluid; A hydraulic pump for sucking the working fluid from the storage tank to discharge the working fluid by increasing the pressure; It has a first and a second inlet / outlet and an output shaft, the working fluid is supplied from the hydraulic pump to one of the first and second inlet / outlet through one of the first and second fluid supply / discharge passage And discharge from the other of the first and second inlet / outlets to the storage tank through the other of the first and second fluid supply / discharge passages, and the output rotating shaft is a working fluid from the hydraulic pump. A hydraulic motor which rotates in one direction when the first inlet / outlet is received and the output shaft rotates in the opposite direction when the working fluid from the hydraulic pump is received by the second inlet / outlet; And a brake piston engageable with the output rotation shaft of the hydraulic motor, wherein the cylindrical casing has a brake spring for elastically pressing the brake piston to engage the output piston of the hydraulic motor and the brake piston that is slidably received. And the brake piston and the cylindrical casing jointly form a main hydraulic chamber through which a working fluid is supplied through the fluid opening passage, and the working fluid is discharged through the fluid opening passage, and the brake piston is formed within the main hydraulic chamber. A pressure portion of the working fluid has a first piston area portion applied to disengage the brake piston from the output shaft of the hydraulic motor with respect to the elastic force of the brake spring, the output shaft of the hydraulic motor being hydraulic oil When the sieve is discharged from the main hydraulic chamber of the mechanical brake assembly, it is mechanically braked by the elastic force of the brake spring through the brake piston, and the output shaft of the hydraulic motor has a working fluid in the main hydraulic chamber of the mechanical brake assembly. A mechanical brake assembly adapted to be released from the brake piston by fluid pressure in the main hydraulic chamber when supplied to the main hydraulic chamber; Provided on the first and second fluid supply / discharge passages to have the fluid open passage selectively maintained in fluid communication with the first and second fluid supply / discharge passages, and in fluid communication with the fluid open passage. A working valve in one of the first and second fluid supply / discharge passages maintained in a state may have a higher pressure than a working fluid in the other of the first and second fluid supply / discharge passages; It is provided on the first and second fluid supply / discharge passage, the working fluid is supplied from the hydraulic pump to the first fluid supply / discharge passage and from the second fluid supply / discharge passage to the storage tank A first directional control valve position to be discharged, a second directional control valve position to allow the working fluid to be discharged from the first and second fluid supply / discharge passages to the storage tank, and a working fluid to the A directional control valve operative to determine three different directional control valve positions comprising a third directional control valve position to be supplied to a second fluid supply / discharge passage and to be discharged from the first fluid supply / discharge passage; And The hydraulic motor is provided on the first and second fluid supply / discharge passages between the hydraulic pump and the directional control valve, and the hydraulic motor is operated while the directional control valve is displaced to determine the second directional control valve position. A counterbalance valve operative to prevent pressurization of the working fluid by the hydraulic motor during one of the first and second fluid supply / discharge passages; It consists of The brake piston and the casing further form a secondary hydraulic chamber, and the brake piston has a second piston area portion in which the pressure of the working fluid in the secondary hydraulic chamber is applied against the elastic force of the brake spring; , The hydraulic system is provided on the first and second fluid supply / discharge passages, and a working fluid flows between the first fluid supply / discharge passage and the secondary hydraulic chamber via a fluid transfer / return passage. A first selection valve position in which flow is interrupted between the second fluid supply / discharge passage and the secondary hydraulic chamber via the fluid transfer / return passage, and a working fluid supply the first fluid through the fluid transfer / return passage A second selector valve position at which flow is interrupted between the discharge passage and the secondary hydraulic chamber and between the second fluid supply / discharge passage and the secondary hydraulic chamber, and a working fluid transfers the fluid / A return passage flows between the second fluid supply / discharge passage and the secondary hydraulic chamber and the first fluid supply / discharge passage passes through the fluid transfer / return passage. And further comprising a selector valve operable to determine three different valve positions consisting of a third selector valve position at which flow is interrupted between the secondary hydraulic chambers, the selector valve actuating within the first fluid supply / discharge passage. When the pressure of the fluid is less than the pressure of the working fluid in the second fluid supply / discharge passage, the first selector valve is operated to determine the position of the first selector valve, the selector valve being the pressure of the working fluid in the first fluid supply / discharge passage And when the pressure of the working fluid in the second fluid supply / discharge passage is equal to the pressure of the working fluid in the first fluid supply / discharge passage, the selector valve is operated. 2 is operated to determine the third selector valve position when greater than the pressure of the working fluid in the fluid supply / discharge passage; and And the hydraulic system further comprises a brake resistor restrictor provided on the fluid transfer / return passage to limit the flow of working fluid in the fluid transfer / return passage. 12. The first control valve position and the working fluid of claim 11, wherein the first control valve position and the working fluid are provided on the fluid opening passage, and a working fluid flows through the fluid opening passage between the shuttle valve and the main hydraulic chamber. And a control valve operative to determine two different control valve positions consisting of second control valve positions adapted to be discharged from said main hydraulic chamber to said storage tank via an open passage. The first check valve provided on the first fluid supply / discharge passage, and the working fluid to allow the working fluid to flow only from the direction control valve to the first inlet / outlet of the hydraulic motor. A second check valve provided on the second fluid supply / discharge passage to flow only from the direction control valve to the second inlet / outlet of the hydraulic motor, The first fluid supply / discharge passage is separated by the first check valve into a hydraulic motor side passage portion and a directional control valve side passage portion, and the second fluid supply / discharge passage is a hydraulic motor side passage portion and a direction control valve. Separated by the second check valve into the side passage portion, The counterbalance valve includes first and second valve spools arranged in alignment with each other and each having an inner end facing each other and an outer end remote from each other, The valve casing has the first and second valve spools slidably received, the inner end of the first and second valve spools and the valve casing are in a central hydraulic chamber maintained in fluid communication with the fluid opening passage. And the outer end portion of the first valve spool and the valve casing jointly form a first side hydraulic chamber maintained in fluid communication with a passage portion of the directional control valve side of the first fluid supply / discharge passage. And the outer end portion of the second valve spool and the valve casing jointly form a second side hydraulic chamber maintained in fluid communication with a passage portion of the direction control valve side of the second fluid supply / discharge passage, A first return spring pressurizes the first valve spool to move toward the second valve spool, A second return spring pressurizes the second valve spool to move toward the first valve spool, The first restrictor is adapted to restrict the flow of the working fluid between the first side hydraulic chamber and the passage control valve side passage portion of the first fluid supply / discharge passage. It is provided between the passage part and the directional control valve side of the supply / discharge passage, The second restrictor is adapted to restrict the flow of working fluid between the second side hydraulic chamber and the passage control valve side passage portion of the second fluid supply / discharge passage. It is provided between the passage part and the directional control valve side of the supply / discharge passage, A third restrictor is provided between the central hydraulic chamber and the fluid opening passage to restrict the flow of working fluid between the central hydraulic chamber of the counterbalance valve and the fluid opening passage, The first valve spool of the counterbalance valve allows a working fluid to flow between the hydraulic motor side passage portion of the first fluid supply / discharge passage and the directional control valve side passage portion of the first fluid supply / discharge passage. Spool where the first spool position and the working fluid are blocked from flow between the hydraulic motor side passage portion of the first fluid supply / discharge passage and the directional control valve side passage portion of the first fluid supply / discharge passage Axially movable to determine two different spool positions of position, The second valve spool of the counterbalance valve allows a working fluid to flow between the hydraulic motor side passage portion of the second fluid supply / discharge passage and the directional control valve side passage portion of the second fluid supply / discharge passage. Spool where the first spool position and the working fluid are blocked between the hydraulic motor side passage portion of the second fluid supply / discharge passage and the directional control valve side passage portion of the second fluid supply / discharge passage Axially movable to determine two different spool positions of position, The working fluid is the hydraulic motor side passage portion of the first fluid supply / discharge passage and the hydraulic motor side passage of the second fluid supply / discharge passage when the first and second valve spools are respectively moved to determine the first spool position. Between the part and the counterbalance valve, and the working fluid is the hydraulic motor side passage of the first fluid supply / discharge passage when the first and second valve spools are moved to determine the second spool position, respectively. Between the portion and the hydraulic motor side passage portion of the second fluid supply / discharge passage is blocked by the counterbalance valve, The first valve spool of the counterbalance valve has hydraulic pressure of the working fluid applied to the inner end of the first valve spool and the hydraulic pressure of the working fluid applied to the outer end of the first valve spool and the first return spring. The first valve spool of the counterbalance valve is moved by the hydraulic force of the working fluid applied to the inner end of the first valve spool when the first spool position is greater than the sum of the elastic forces of the first spool. Is moved to determine the second spool position when less than the sum of the hydraulic force of the working fluid applied to the outer end of the first spring and the elastic force of the first return spring, The second valve spool of the counterbalance valve has hydraulic pressure of the working fluid applied to the inner end of the second valve spool and the hydraulic pressure of the working fluid applied to the outer end of the second valve spool and the second return spring. The second valve spool of the counterbalance valve is moved to determine the second spool position when the elastic force of the second spool is greater than the sum of the elastic forces of the hydraulic fluid applied to the inner end of the second valve spool. And the hydraulic pressure of the working fluid applied to the outer end of the hydraulic system is smaller than the sum of the elastic force of the second return spring to determine the second spool position. The counterbalance valve of claim 13, wherein the first valve spool of the counterbalance valve further determines a third spool position between a first spool position and a second spool position of the first valve spool, and the counterbalance valve Wherein the second valve spool further determines a third spool position between a first spool position and a second spool position of the second valve spool, and a working fluid is such that the first and second valve spools are respectively Characterized in that it flows between the hydraulic motor side passage portion of the first fluid supply / discharge passage and the hydraulic motor side passage portion of the second fluid supply / discharge passage when moved to determine the third spool position. Hydraulic system.